Thread-milling machine

ABSTRACT

A thread milling machine comprising: a base; a work head and a cutter head mounted on said base, each of said heads having means to rotate, respectively, a workpiece and a cutter on parallel axes; means on said cutter head for advancing the work piece axially; and means on said work head for periodically reciprocating the work transversely of its axis of rotation.

United States Patent [72] Inventor Bror W. Swanson 1,155,432 l0/1915Muller 90/11.54 81 Rumiord St., West Hartford, Conn. 1,343,503 6/1920Hall 90/1 1.54 06607 1,863,570 6/1932 Lees 90/1 1.54 [2]] Appl. No.772,699 3,023,546 3/1962 Beck 90/1 1.54 [22] Filed Nov. 1, 1968 1Patented J 1971 Primary Examiner-Gil Weidenfeld Attorney-Berman,Davidson & Berman [54] THREAD-MILLING MACHINE 8 Claims, 4 Drawing Figs.

[52] U.S.Cl 90/1L54, 90/21;10/105 [51] Int. Cl 823g l/32 ABSTRACT: Athread milling machine comprising: a base; a [50] Field of Search 90/11.54. work head and a cutter head mounted on said base, each of 1 1.5, 11.4, 21; 10/105 said heads having means to rotate, respectively, aworkpiece and a cutter on parallel axes; means on said cutter head forad- [56] References C'ted vancing the work piece axially; and means onsaid work head IT D S ATE PAT NT for periodically reciprocating the worktransversely of its axis 54,096 4/1866 Bee 90/1 1.54 Of rotation- 1' 341 r 3 F 68 50 22 2 E I 4 52 52 1 F 7 2 0 70 I i 3 2 62 74 5 i :3 I 54iin I 1 7o 66 l 1 86 l 5. r a g 7n 60 4 1 i I 28 23 J L 11111 a? 2THREAD-MILLING MACHINE It is a primary object of this invention toprovide a machine for milling the cutting edges on thread-cutting tapsand dies from initially fluted blanks. Such. a machine is also welladapted ,to make certain precision aircraft parts.

It is a further object of this invention to provide a machine asaforesaid which will be fully automatic in operation and which may bequickly and easily adapted for the production of taps or dies of anyselected pitch or diameter.

It is a further object of this invention to provide a machine asaforesaid which will complete its milling operation with a minimumnumber of rotations of the workpiece.

The above and other objects will be made clear from the fol-,

lowing detailed descriptiontaken'in connectionwith theannexeddrawingsjn'whichz of this machine, reference should be made toFIG. 4.,The

machine is presented with a workpiece in the form of the dotted circle10 in which have been formedflutes 12 which usually will be axiallystraight but for some purposes may be formed as ,a spiral. The shankportion is indicated by the dotted line 14. The blank on which themachine will operate therefore consists of a cylindrical portioncorresponding to the circle 10 and grooved as shown at 12 connected to ashank portion 14 of lesser diameter. Details of the shank, of course,are dictated by the machine in which the tap is to be used and thereforeconcern thisinvention not at all.

The edges 16 are cut so as to present in' cross section having a profileof the female thread to be formed by the tap. The edges 16 must includerelief to the rear of the front'cutting edges l8,'as indicated by thearrows u-a in FIG. 4-. All of this is conventional tap design but itwill clearly be seen that the problem of milling the tap to produce theteeth shown in FIG. 4 is by no means a simple problem.

Referring now to FIG. 1, the machine as a whole is mounted on a base 20.The work head 22' is slidably mounted on an intermediate base 24 whichinr'turn is slidably mounted on a subbase '26. The head 22 slides on theintermediate base 24 and is of the cutter 36 ona subbase38. The subbase38 is itself slidable parallel to the, axis of the cutter 360a a mainbase40. Sliding the cutter head: transverse the axis is under control ofa hydraulic cylinder-42 and axial slidingof the subbase 48 is under thecontrolof a hydraulic. cylinder The motor 34 has infinitely variablespeediwithin the limits of its electronic control. Since the cutter headand its mounting andits motor constitute purely conventional design,these parts will not have furtherdetailedidescription.

As seen in FIG. 1, a1worm:gear50'is mounted: inthe work. head 22' ontaperedopposedroller bearings S2iwhi'ch have the effect of locking thewormzgear 50. against axial movement. Keys 54 form a slidable splineconnectionbetween the gear 50 and a work shaft'56which hasan-enlargedend 58with both ends having bearing in the work headr2-2.'A gear issecured to and rotatable with; the enlarged end 58 for a purposepresently tobedescribed;

The left-hand end of the. work shaft 56. has a reduced portion62iconnectedby-a key 64 with a threaded sleeve-66. The threads on thesleeve64'mate with threads formed on a female sleeve 66 havinga flange68 bolted or otherwise secured tothe work head 22. Thereducedportion=62of the shaft 56 has a further reduced threaded end70=which receives a locknut 72 l which holds the sleev el60tirmlyagainst a shoulder 74 which forms the demarcation between theshaft 56 and the reduced portion 62. As aresult, as the shaft 56 isrotated, the sleeve 60 advances along itsthreads'by virtue of engagementwit-h the female sleeve 66, thereby advancing the shaft 56 axiallytoward the working end.. The rate of advance depends, of course, on thepitch of the threads between the sleeves 60 and 66 with a different'pairof sleeves being required for each particular pitch of the work to bemilled,

At the opposite end a chuck 76 is securpd carrying the conventionalthree jaws 78 for-gripping the shank l4 (FIG. 4) of a workpiece 10.

Referring now to FIGS. 1 and'2, it will be seen that the gear 70 mesheswith a lower gear 80 mounted on a shaft 82 which, as indicated at 84 inFIG, 1, hasbearing in the work head 22. Also secured to the shaft 82 forrotation therewith is a cam 86. The cam 86 is a very central part ofthis invention and will be described in detail hereinafter.

As seen in FIG. 3, the worm gear 50 meshes'with a worm 88 mounted inopposed tapered bean'ngs 90 in the base of the work head 22. Thisarrangement of bearings, like that of the bearings 52, locks the worm 88against axial movement. The worm is mounted on the shaft 92 and isrotated by a motor 94 also mounted on the work head 22. The motor 94,within its range, has infinitely variable speed under electroniccontrol. Such controls are now conventional and need not be discussedhere.

A comparison of FIGS. I and 2shows the work head 22 as slidable on theintermediate base 24. A lug 96 is mounted at the left-hand end of theintermediate base 24. A shaft 98 is rotatably mounted in the lug 96 andhas a hand wheel 100 at one end with its opposite end threaded, asindicated at 102, with the threaded end engaging mating threads in thework head 22. This permits adjustment of the work head 22 on theintermediate base 24 in a direction transverse the axis of the chuck 76.This adjustment is necessary to take care of varying diameters of theworkpiece l0 and of the cutter tool 36, the adjustment being made whenthe diameters of the workpiece and 'of the cutter are determined. Aspreviously noted, the subslide 24-is itself slidable on the subbase 26.The subbase 26 has a bracket 104 at the free end of which a rollerfollower 106 is mounted to engage the cam 86. The bracket 104 is securedin an elongated slot 108 in the subbase'26 by means of bolts 1 10. Thisenables the follower 106 always properly to engage any particular cam86.

- At the right-hand end the subbase 26 there is formed an upwardlyprojecting lug 112. A compression spring 114 engages at one end with thelug 112 and with the intermediate base 24 within a recess 116. Thespring 114 maintains contact between the follower I06 and the cam 86 so,as the cam 86 rotates, the intermediate base 24 and the cutter head 22will reciprocate to left and right, as viewed in FIG. 2, the amount andrapidity-of motion depending on the contours of the particular cam 86.

The precise contours of the cam 86' are chosen with respect to thenumber of teeth on the tap or die to be milled, the number of flutesinthe workpiece 10', and particularly with reference to the formation ofthe clea ance on the line (1-0 of FIG. 4. Cam 86'of FIGS. 1 and 2 isdesigned for straight axial flutes 12 formed in the workpiece 10. Itcan, of course, be adapted to cut tapered taps and to accommodatehelical flutes.

Each particular tap or die to be milled will require a particular malethreadedsleeve 60, a particular female sleeve 66 and a particular cam'86. It is to be noted that all adjustments-transverse the axes ofrotation are made through the work head 22, the-intermediate base 24 andthe subbase 26 whileall axial adjustments are made by the subslide 38supporting the cutter head 32. The transaxial motion of the cutter head32 occasioned'by the hydraulic cylinder 42- is used primarily to movethe cutter head 32out of the way between operations or during a changeof cams and sleeves.

. I claim:

l. A thread-milling machine comprising: a base; a work head and a cutterhead mounted on said base, each of said heads having means to rotate,respectively. an axially fluted workpiece and a cutter on parallel axes;means on said work head to provide a predetermined advancement of theworkpiece axially of said cutter for each rotation of said workpiece;and means on said work head for periodically reciprocating the workpiecetransversely of its axis of rotation a predetermined plurality of timesduring each said predetermined axial advancement of the workpiece.

2. A thread-milling machine comprising: a base; a work head and a cutterhead mounted on said base, each of said heads having means to rotate,respectively, a workpiece and a cutter on parallel axes; means on saidwork head for advancing the workpiece axially; and means on said workhead for periodically reciprocating the work transversely of its axis ofrotation, said machine including a subbase; an intermediate baseslidable on said subbase, said intermediate base slidably supportingsaid work head; a cam rotatable on said work head; a follower mounted onsaid subbase and engaging said cam and resilient means operable betweensaid work head and said subbase for biasing said cam and follower intomutual engagement.

3. The machine of claim 1, including a shaft in said work head, meansslidably connecting said shaft and said workpiece rotating means forrotating said shaft, said shaft carrying'a chuck for holding saidworkpiece; said axially advancing means including threaded means on saidshaft; threaded means on said work head mating with said threaded meanson said shaft whereby to advance said shaft, said chuck and saidworkpiece axially as said shaft rotates.

4. The machine of claim 3, in which the threaded means on the shaftcomprises an externally threaded sleeve keyed to the shaft and thethreaded means on the cutter head comprises a flanged, internallythreaded sleeve, said flange being bolted to the work head.

5. The machine of claim 3, in which said cam has spaced, peripherallobes, each lobe being profiled in accordance with the thread desired onsaid workpiece.

6. The machine of claim 2, including a shaft in said work head, meansslidably connecting said shaft and said workpiece rotating means forrotating said shaft, said a shaft carrying a chuck for holding saidworkpiece; threaded means on said shaft; threaded means on said workhead mating with said threaded means on said shaft whereby to advancesaid shaft, said chuck and said workpiece axially as said shaft rotates.

7. The machine of claim 6, in which the threaded means on the shaftcomprises an externally threaded sleeve keyed to the shaft and thethreaded means on the cutter head comprises a flanged, internallythreaded sleeve, said flange being bolted to the work head.

8. The machine of claim 6, in which said cam has spaced. peripherallobes, each lobe being profiled in accordance with the thread desired onsaid workpiece.

1. A thread-milling machine comprising: a base; a work head and a cutterhead mounted on said base, each of said heads having means to rotate,respectively, an axially fluted workpiece and a cutter on parallel axes;means on said work head to provide a predetermined advancement of theworkpiece axially of said cutter for each rotation of said workpiece;and means on said work head for periodically reciprocating the workpiecetransversely of its axis of rotation a predetermined plurality of timesduring each said predetermined axial advancement of the workpiece.
 2. Athread-milling machine comprising: a base; a work head and a cutter headmounted on said base, each of said heads having means to rotate,respectively, a workpiece and a cutter on parallel axes; means on saidwork head for advancing the workpiece axially; and means on said workhead for periodically reciprocating the work transversely of its axis ofrotation, said machine including a subbase; an intermediate baseslidable on said subbase, said intermediate base slidably supportingsaid work head; a cam rotatable on said work head; a follower mounted onsaid subbase and engaging said cam and resilient means operable betweensaid work head and said subbase for biasing said cam and follower intomutual engagement.
 3. The machine of claim 1, including a shaft in saidwork head, means slidably connecting said shaft and said workpiecerotating means for rotating said shaft, said shaft carrying a chuck forholding said workpiece; said axially advancing means including threadedmeans on said shaft; threaded means on said work head mating with saidthreaded means on said shaft whereby to advance said shaft, said chuckand said workpiece axially as said shaft rotates.
 4. The machine ofclaim 3, in which the threaded means on the shaft comprises anexternally threaded sleeve keyed to the shaft and the threaded means onthe cutter head comprises a flanged, internally threaded sleeve, saidflange being bolted to the work head.
 5. The machine of claim 3, inwhich said cam has spaced, peripheral lobes, each lobe being profiled inaccordance with the thread desired on said workpiece.
 6. The machine ofclaim 2, including a shaft in said work head, means slidably connectingsaid shaft and said workpiece rotating means for rotating said shaft,said a shaft carrying a chuck for holding said workpiece; threaded meanson said shaft; threaded means on said work head mating with saidthreaded means on said shaft whereby to advance said shaft, said chuckand said workpiece axially as said shaft rotates.
 7. The machine ofclaim 6, in which the threaded means on the shaft comprises anexternally threaded sleeve keyed to the shaft and the threaded means onthe cutter head comprises a flanged, internally threaded sleeve, saidflange being bolted to the work head.
 8. ThE machine of claim 6, inwhich said cam has spaced, peripheral lobes, each lobe being profiled inaccordance with the thread desired on said workpiece.